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TESTGIRGUIT FOR MULTIPLE SWITCH BOARDS.

No. 427,120. Patented May '6; 1890.

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TEST CIRCUIT FOR MULTIPLE SWITCH BOARDS. No. 427,120. Patented May 6, 1890 h J j Zfla zizwawx F inventor. lf ymlfiflover. v

UNITED STATES ATENT Orric.

, CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

TEST-CIRCUIT FOR MULTIPLE SWITCH-BOARDS.

SPECIFICATION forming part of Letters Patent No. 427,120, dated May 6, 1890.

Application filed December 27, 1886.

To all whom it may concern:

Be it known that 1, CHARLES E. SORIBNER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Test-Circuits for Multiple Switch-Boards, (Case 120,) of which the following is a full, clear, concise, and exact description, reference being had to the accom- Io panying drawings, forming a part of this specification.

My invention relates to multiple switchboard systems of a telephone-exchange; and its object is to provide a uniform test whereby I 5 ;it may be determined at one board Whether another line, whether single or metallic, is in useor connected at any other of the boards.

Heretofore many different test-circuits have been invented. The one most commonly in 201156 is described and claimed in my patent,

No. 305,021, of September 9, 1884. The system therein described is primarily designed for use in connection with ground-circuits. W'hen metallic circuits are used, in order that there may be a uniform test for metallic circuits and ground-line circuits it has heretofore been thought necessary to employ special test-circuits, one for each metallic circuit as well as for each ground-circuit, with 0 separate test pieces and connections upon the different boards.

By the use of my invention herein I am enabled to make the test the same, whether the line tested be a metallic circuit or a ground- 3 5 circuit, and without the use of the additional or special test-circuits for the different telephone-lines, as heretofore, the spring-jacks which I use having preferably the same number of contact-points as those shown in my said patent.

A feature of my invention is a circuitbreaker, one circuit-breaker being included in each line between the contact-point on the spring-jack of the last board and the test piece or frame of said spring-jack. These circuit-breakers are driven constantly in any suitable manner, so that as long as no plug is inserted in any spring-jack of a line the circuit of said line will be continuously interrupted. On inserting a plug in a spring=jack of any line the portion of the line containing Serial No. 222,698. (No model.)

the circuit-breaker will be left dead open at the spring-jack in which the plug is inserted, and thus the circuit-breaker will have no effect upon the line. 5 5

When metallic circuits are used, the branch or side of the circuit which connects with the frames or test-pieces of the switches of the line extends to the subscribers station, and is there normally open. In case ground-cir- 6o cuits are used, the line is connected with the subscribers outfit in the usual manner, and extends thence through the switches of the line and back to the test pieces or frames, and after passing through the test-pieces through resistance to ground. Metallic and ground circuits thus connected may be used as desired upon the same switch-boards. The individual annunciator is preferably placed next to the circuitbreaker in each line, so that it will come in the wire between the point of the last spring-jack and the frame or test piece of said spring-jack.

In my patent, No. 383,495, granted May 29, 1888, application for which was filed simul- 7 5. taneously with this, I have described and claimed an invention to enable operators at different boards to test to determine whether any line is busy when said lines are connected with ordinary spring-jack switches and without the use of special testwires and special connections therefor.

In another application filed upon the same day, Serial No. 222,706, now pending, I have described an invention which consists, essentially, in placing a buzzer in circuit with the individual annunciatorin each line in combination with circuits and testing apparatus, by means of which, when a test is made, the buzzer will cause a tone in the telephone if 0 the line tested is free.

tional view of the loop-plug which is used in connection with the double-stranded cords of the key-board apparatus.

The metallic circuit is shown connected with the spring-jacks a and Z) upon the different boards in Fig. 1. The ground-circuit is shown connected with the spring-jacks c and (1 upon the different boards. .It will be observed that the connections with spring-jacks a b are the same as the connections with spring-jacks 0 cl, the only difference in the circuits being that the wire connecting with the frames of spring-jacks a 1) extends back to the subscribers station, while the wire connected with the frames or test pieces of switches 0 cl passes through resistance 6 at the central ofiice to ground. The metallic circuit may be traced from ground f at the subscribers station (see Fig. 2) through the generator and bell to the subscribers switch g, and thence by branch it back to the subscribers station (see Fig. 1) and through the spring-jacks a b, and from the point of the last spring-jack by wire 2' through the circuitbreaker is and the annunciator to branch Z, which branch Z is connected with the frames of the switches a b and extends to the subscribers station, where said branch Z is normally open. Branch Z at the subscribers station is connected through the telephone, and from the line side of the telephone there is a connection to a switch for closing branch Zto ground when the subscriber sends current to line by turning his generator.

The ground-line m is connected, as shown, through the switches c d, and thence by wire 'n through the circuit-breaker 0 and the annunciator back to the frames of said switches 0 cl, and through resistance 6 to ground at the subscribers station.

It should be noted that branch Z of the metallic circuit being open at the subscribers station, its resistance will be infinite. The resistance 6, however, in the test portion n of the ground-circuit is high enough, so that when a connection is made with the test-wire n at the frame of any spring-jack sufficient current will be shunted from line m through the telephone thus connected at the frame of any spring-jack of the line.

The key-board apparatus which I have shown forms the subject-matter of an application filed herewith, being my Case No. 119. I shall therefore describe the key-board apparatus only incidentally herein. It is evident that other key-board systems might be used successfully in connection with my testcircuits.

I will now describe the manner of testing to determine whether a line called for at the board is in use or connected at any other board.

.ing the test-piece of switch a. Since the portion 2' of the metallic circuit is open at switch b, the circuit-breaker 7t will not interrupt the circuit of telephone q when plug 19 is thus touched to the test-piece of switch ct, as shown. Thus the metallic circuit being in use when a plug 19 connected. with a telephone q and test-battery is applied to any switch of the line at any other board, no rattling caused by the circuit-breaker it .will be heard in telephone q; hence the operator listening at telephone q will know that the line is busy when he hears no rattling in said telephone g. In like manner, if the tip or plug p be applied to the frame of switch 0 of the grounctcircuit as long as the ground-circuit is open, as shown at switch d, the portion 72 of said ground-circuit which contains the circuitbreaker 0 being open, the circuit-breaker will have no effect to interrupt the circuit through the telephone g, and the operator listening at said telephone g by the absence of any rattling in his telephone will know that the ground-line is in use. Thus the same signal indicates busy,whether the test be applied to the metallic circuit or the ground-circuit.

We will suppose now that the plugs are removed from switches b (1, so that both lines will be free. In this case the tip of plug 19 is touched to the frame or test piece of switch a, as shown, and the circuit will be closed through the telephone (1 and circuit-breaker k, and the interruptions of the circuit caused by circuit-breaker will cause a rattling, which will indicate that the line is free. This circuit may be traced from the ground-plate r to the heel of the plug resting thereon, and thence through strand .9 of the cord through the loopswitch and test-battery and telephone q, as shown, to the tip of the plug 19, and thence to the frame of switch. a, and thence through line 71 and the circuit-breaker to branch h of the metallic circuit, and over said branch h to the subscribers switch-lever and thence through the bell and generator to ground f at the subscribers station. Thus when no plug is inserted in any switch of the line and a plug 1) is applied to the test-plate of any switch upon either of the boards the circuit breaker It will be included in circuit with the test-battery and telephone g and the operator will know by the rattling caused in his telephone by the interruption of the circuit that the line is free, andin like manner when a test is made at one of the switches of the ground-line m a rattling will be heard in the operators telephone if said ground-line is not busy.

We will suppose the plug removed from switch d and the tip of plug 19 resting upon the test-plate of switch C-' In such case the circuit would be traced as before, from groundplate 7" through the strand 8 of the flexible cord, the telephone 1 and test-battery being looped in said strand 5 to the frame of switch 0, and by test branch at connected with said frame through the circuitbreaker 0, and

thence to line m and to ground at the subscribcrs station. Since resistance 6 is in= claim as new and desire to secure by Lettersv Patent- 1. A telephone-line connected with ground at the subscribers station and extending through a switch on each of two or more switch-boards, a circuit-breaker, and a con-- nection from said circuit-breaker to the frames 4 or test pieces of the switches of the line, in combination with a branch circuit to ground at each board, including a telephone and test battery, whereby a test may be made at any board to determine Whether the line is in use or connected at any other board.

2. In a multiple switch-board system, the circuit connecting together the springs of several spring-jacks, one upon each board,

another circuit connecting together the testpieces of the said jacks, and a constantlyvibrating circuit-breaker included in the circuit between the frames of the jacks, in combination with a telephone and test-battery, whereby an operator may determine by closing the said telephone to one of the testpieces Whether the line is open at any one of the spring-jack switches.

In Witness whereof I hereunto subscribe my name this 16th day of November, A. D. 1886.

CHARLES E. SCRIBNER.

Witnesses:

GEORGE P. BARTON, WVM. M. GILLER. 

